1. Field of the Invention
The present invention relates to a back lapping in-line system for semiconductor device fabrication, and more particularly, to a back lapping in-line system for carrying out an array of processes in-line, including vinyl covering, back side grinding, and vinyl removing.
2. Background of the Related Art
Generally, semiconductor wafers are processed into packages, and before the package process, the back side of the wafer is ground. The array of processes including the back side grinding is called "back lap" or "back grind".
FIG. 1 shows a conventional back lap process, including back side grinding using a grinder carried out between a wafer fabrication process 10 and an assembly process 22. The back lap process comprises a pre-process for back side grinding 12, a vinyl covering 14, a back side grinding 16, a vinyl removing 18, and a process after back side grinding 20.
The vinyl covering step 14 covers the front side of the wafer with vinyl in order to protect the front side of the wafer with the pattern formed thereon from silicon particulate produced during the back side grinding 16. The vinyl removing step 18 removes the vinyl from the wafer surface, since the vinyl is no longer needed after the back side grinding 16.
In the back side grinding 16, the back side of the wafer is ground using a diamond wheel, and frictional heat is generated during the back side grinding. The wafer may become warped by this heat, causing warpage failure.
The larger the wafer, the more serious the warpage failure, which causes errors in loading and unloading of wafers on a cassette. Sometimes, the warpage failure renders the wafer unusable.
FIG. 2 shows a structure of a conventional facility in which the vinyl covering, back side grinding, and vinyl removing shown in FIG. 1 can be carried out.
Referring to FIG. 2, a network line 30 is connected to manual interfaces 32, 34 and 36, which connect to a laminator 38 to carry out the vinyl covering, a back grinder 40 for the back side grinding, and a remover 42 for the vinyl removing, respectively.
The laminator 38 comprises: a loading part 44, a pre-cut part 46, a centering part 48, a wire cut part 50, and an unloading part 52. The back grinder 40 comprises: a loading part 54, a centering part 56, a grinding part 58, a cleaning part 60, and an unloading part 62. The remover 42 comprises: a loading part 64, a centering part 66, a UV (ultra violet) irradiation part 68, a removing part 70, and an unloading part 72.
The laminator 38, the back side grinder 40, and the remover 42 are connected to a host computer (not shown), or other facility, via their own manual interfaces 32, 34 and 36, respectively, so as to communicate information and carry out their corresponding operations.
However, the laminator 38, the back side grinder 40, and the remover 42 of the conventional facility have their own loading and unloading parts as shown in FIG. 2; that is, there are common elements in each facility unit.
As a result, time is lost in the conventional facility while loading and unloading at each part. Furthermore, the facility requires temporary holding areas for transferring wafers between the laminator 38 and the back grinder 40, and between the back grinder 40 and the remover 42, respectively, thereby requiring additional work space.
In case of a wafer which has a warpage failure after back side grinding, there is a higher risk of it being scratched or broken due to its warped state while it passes through three loading and unloading steps, thereby decreasing production yield.
That is, the conventional facility for back side grinding has problems which decrease productivity, wherein first, wafers are under a higher risk of being damaged during their loading or unloading because the wafers are loaded or unloaded multiple times; second, the conventional facility needs holding space because each unit process is carried out in its corresponding separate facility unit; and third, TAT (Turn Around Time) is longer in the conventional facility because continuity is lost between facility units while performing one single run, and a process can be carried out only after the previous process has been completed.